Locatable catheter

ABSTRACT

A catheter having a sensor at a distal end thereof, useable to detect and create signals from an electromagnetic field. The sensor is constructed and arranged to leave a lumen of the catheter open such that it may be used to pass instruments therethrough once a target location has been reached.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patent Ser. No.14/109,244 filed on Dec. 17, 2013 by Greenburg et al., which is acontinuation application of U.S. patent Ser. No. 12/755,332 filed onApr. 6, 2010 by Greenburg et al., now U.S. Pat. No. 8,611,984, whichclaims priority to U.S. Provisional Application Ser. No. 61/167,839filed Apr. 8, 2009 entitled Locatable Catheter, which are herebyincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The field of the present invention pertains generally to the navigationof a device, such as a catheter, through a branched structure and themonitoring of a position of said device once a target location has beenreached. More specifically, the present invention relates to a locatablecatheter for navigating through body lumens and providing a deliveryconduit for other devices.

BACKGROUND OF THE INVENTION

The most common interventional procedure in the field of PulmonaryMedicine (i.e., medicine pertaining to the respiratory system) isbronchoscopy, in which a bronchoscope is inserted into the airwaysthrough the patient's nose or mouth. The structure of a bronchoscopegenerally includes a long, thin, flexible tube that typically containsthree elements: an illumination assembly for illuminating the regiondistal to the bronchoscope's tip via an optical fiber connected to anexternal light source, an imaging assembly for delivering back a videoimage from the bronchoscope's distal tip, and a lumen or working channelthrough which instruments may be inserted, including but not limited todiagnostic (e.g., biopsy tools) and therapeutic (e.g., laser, cryo or RFtissue elimination probes) instruments. The distal tip of a bronchoscopeis steerable and therefore rotating a lever placed at the handle of thebronchoscope actuates the steering mechanism by deflecting the tip intwo opposite directions.

Bronchoscopes are limited, however, in how far they may be advancedthrough the airways due to their size. Typically, a bronchoscope is muchwider than other types of catheters, mainly due to the size constraintsplaced on their design by the camera. Unfortunately, the lesion ortarget of interest is often located deeper in the lungs than abronchoscope can travel. Hence, three-dimensional location technologyhas been developed that allow the navigation of a steerable catheterdeep into the lungs. The catheter includes a sensor that can be detectedmagnetically with great precision. Of particular relevance to thepresent invention are the devices and methods described in the followingreferences: PCT Patent Publication No. WO 03/086498 entitled “EndoscopeStructure and Techniques for Navigation in a Branched Structure” toGilboa; U.S. Pat. No. 7,233,820 entitled “Endoscope Structures AndTechniques For Navigating To A Target In Branched Structure” to Gilboa;U.S. Pat. No. 6,947,788 entitled “Navigable Catheter” to Gilboa; U.S.Pat. No. 6,833,814 entitled “Intrabody Navigation System For MedicalApplications” to Gilboa et al.; U.S. Pat. No. 6,711,429 entitled “SystemAnd Method For Determining The Location Of A Catheter During AnIntra-Body Medical Procedure” to Gilboa et al.; U.S. Pat. No. 6,615,155entitled “Object Tracking Using A Single Sensor Or A Pair Of Sensors” toGilboa; U.S. Pat. No. 6,593,884 entitled “Intrabody Navigation SystemFor Medical Applications” to Gilboa et al.; U.S. Pat. No. 6,380,732entitled “Six-Degree Of Freedom Tracking System Having A PassiveTransponder On The Object Being Tracked” to Gilboa; U.S. Pat. No.6,188,355 entitled “Wireless Six-Degree-Of-Freedom Locator” to Gilboa;each of which is hereby incorporated by reference in its entirety.

These references describe methods and devices in which locatable guides(“LGs”), enveloped by sheaths, are used to navigate to a location withinthe lung. The guide/sheath combination is inserted into the lung via theworking channel of a bronchoscope. Once the tip of the guide is locatedat its target, a lock, which is placed at the orifice (“connectionport”) of the bronchoscope's working channel, is operated to prevent thesheath from sliding in or out of the bronchoscope. The guide is thenwithdrawn from the sheath, leaving the sheath in place to guide a toolto the required target location.

Once the target has been reached with the LG, the LG is removed, leavingthe sheath in place as a conduit to the target for other tools. However,the present design includes most or all of the location technology onthe LG. Hence, once the LG is removed from the sheath, the physician isassuming that the sheath remains in close proximity to, and pointed at,the target.

OBJECTS AND SUMMARY OF THE INVENTION

The present invention addresses the identified needs by providing alocatable sheath that can be used in conjunction with, or instead of, anLG. Adding a sensor to a sheath adds the complication of maintaining anopen lumen through the sheath. As such, various sensor designs areprovided that do not interfere with the sheath lumen.

One aspect of the present invention provides a catheter sheath with asensor at the distal tip. The sensor is comprised of three coils ofwire, each at an angle to the others but sharing a common center point,in order to reduce the overall longitudinal dimension of the sensor. Byreducing the longitudinal dimension, the impact the sensor has on theflexibility of the distal tip is minimized.

Another aspect of the present invention provides a catheter sheath witha sensor incorporated into a side of the sheath, such that the sensor isoff-center. This design allows the entire sensor to be manufacturedseparate from the catheter and attached later as a component.

Yet another aspect of the present invention provides a sheath with asensor that comprises a single coil at the distal tip and surroundingthe lumen. This design greatly reduces the impact the sensor has on theflexibility of the sheath. The single coil design does not provide thedegrees of freedom that a triple-coil design does but would be used inconjunction with an LG and, after the LG is removed, provides enoughinformation to notify the physician that the sheath has moved out ofposition and needs to be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preferred embodiment of the presentinvention; and,

FIG. 2 is a perspective view of a preferred embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

Turning now to the Figures and first to FIG. 1, there is shown a device10 of the present invention. Device 10 generally comprises a locatableguide (“LG”) 12 and a locatable sheath 20. It is understood thatlocatable sheath 20 could be used with or without LG 12. The LG 12includes a sensor 14 embedded in a distal tip 16 thereof. The distal tip16 is shown with a cutout in order to view the embedded sensor 14.Examples of LG 12 embodiments are shown and described in PCT PatentPublication No. WO 03/086498 entitled “Endoscope Structure andTechniques for Navigation in Branched Structure” to Gilboa, which ishereby incorporated by reference in its entirety.

These LG 12 embodiments are steerable probes that incorporate sixdegree-of-freedom (“6 DOF”) sensors that operate by sensingexternally-generated magnetic fields. For example, three magnetic fieldsmay be generated, each using a separate frequency. The three magneticfields vary in intensity throughout an operational area. Placing threeorthogonally-oriented coils in the operational area results in signalsgenerated by the coils that indicate three-dimensional location andthree-dimensional orientation of the sensor 14.

The sheath 20 includes one or more coils 22 that are either embedded inits wall or are attached to an outside surface thereof. The sheath 20also defines a central lumen 24 that is unobstructed by the coils 22.One embodiment of the sheath 20 includes only a single coil 22 proximateits distal tip 26. The coil 22 is used to generate signals indicatingits location in a variety of ways.

For example, the single coil can generate signals using the samemagnetic fields utilized by the LG 12. Hence, after the LG 12 isremoved, the single coil 22 may be used to generate a signal indicatingits three-dimensional location in the operational field.

Alternatively, a field may be generated on a fourth frequency such thatthe sensor 22 may be used concurrently with the sensor 14 of the LG 12.If the sensor 22 is dedicated to a single field on a fourth frequency,the sensor would not be useful for three-dimensional position data butcould be used to generate a signal indicating that it has moved out ofposition after the LG 12 is withdrawn.

Another embodiment, shown in FIG. 1, utilizes multiple coils 22. Thecoils 22 are spaced apart along the length of the sheath 20. The coils22 provide position data of various points along the length of thesheath 20, thereby “painting a picture” of the sheath. As such, eventhough the coils 22 are not providing 6 DOF data, when viewed togetherthey provide an indication of the location and orientation of the sheath20. Hence, this embodiment of sheath 20 may be used to both navigate tothe target and provide a conduit for tools, possibly obviating the needfor the LG 12.

Referring now to FIG. 2, there is shown an embodiment of a sheath 20with a 6 DOF sensor 30 incorporated into its distal tip 26. The sheath20 is shown as transparent such that the details of the sensor 30 may bemore easily displayed. The sensor 30 includes three coils 32, 34 and 36.Coils 32 and 34 are angled, while coil 36 is relatively circumferentialto the sheath 20. Preferably, coils 32 and 34 lie in planes that arerelatively perpendicular to each other. More preferably, all three coilsshare a common center point 38. By sharing a common center point 38, thelongitudinal dimension of the overall sensor is minimized, therebyreducing the impact of the sensor 30 on the flexibility of the sheath20. This design represents an advantage over prior art designs, such asthat shown and described in International Publication Number WO97/29684, to Acker. Acker discloses several coil designs that leave acentral lumen open but are longitudinally extended, resulting in areduced flexibility of the catheter in order to maintain a constantspatial relationship between the coils.

Although the invention has been described in terms of particularembodiments and applications, it should be appreciated that otherembodiments and applications also fall within the scope of the presentinvention. One of ordinary skill in the art, in light of the teaching,can generate embodiments and modifications without departing from thespirit of or exceeding the scope of the claimed invention.

For example, each of the embodiments is described as having sensorsincorporated into a sheath 20 that are passive. In other words, thedescribed sensors generate signals when they pass through magneticfields or reside within an electromagnetic field. However, one skilledin the art will understand that any or all of the coils of the sensorscould be actively energized to generate magnetic fields. The generatedmagnetic fields could then be detected by external passive sensors andused to calculate a position and/or orientation of the coil(s).Accordingly, it is to be understood that the drawings and descriptionsherein are proffered by way of example to facilitate comprehension ofthe invention and should not be construed to limit the scope thereof.

What is claimed is:
 1. A locatable medical instrument insertable througha working channel of a bronchoscope, comprising: a sheath forming alongitudinal lumen along a longitudinal axis of the sheath; and at leastthree coils embedded in a wall of the sheath along the longitudinallumen of the sheath, the at least three coils overlying one another andhaving a common center point, wherein each of the at least three coilsgenerates a signal when placed in an electromagnetic field, wherein oneof the at least three coils forms a plane perpendicular to thelongitudinal axis along the longitudinal lumen, and wherein the othertwo of the at least three coils form two planes, which are angled withrespect to the longitudinal axis and approximately perpendicular to eachother.
 2. The locatable medical instrument of claim 1, wherein thesignal is indicative of a strength of the electromagnetic field and aposition of the sheath.
 3. The locatable medical instrument of claim 1,wherein the at least three coils are positioned proximate a distal endof the sheath.
 4. The locatable medical instrument of claim 1, whereinthe sheath is flexible.
 5. The locatable medical instrument of claim 1,wherein the sheath has a first electromagnetic field sensor embedded ata distal end thereof.
 6. The locatable medical instrument of claim 5,wherein the sheath receives a probe therethrough to position the sheathadjacent target tissue.
 7. The locatable medical instrument of claim 6,wherein the probe has a second electromagnetic field sensor embedded ata distal end thereof.
 8. The locatable medical instrument of claim 7,wherein the first and second electromagnetic field sensors are sixdegree-of-freedom sensors.
 9. The locatable medical instrument of claim8, further including an electromagnetic field generation device forcreating electromagnetic fields having a plurality of frequencies forinducing signals in the first and second electromagnetic field sensors.10. The locatable medical instrument of claim 9, wherein theelectromagnetic field generation device creates electromagnetic fieldsof at least four frequencies, three of the at least four frequenciesdetected by the second electromagnetic field sensor.
 11. A system fornavigating through a branched structure, comprising: a sheath forming alongitudinal lumen along a longitudinal axis of the sheath; at leastthree coils embedded in a wall of the sheath along the longitudinallumen of the sheath, the at least three coils overlying one another andhaving a common center point; and a probe extendable through thelongitudinal lumen of the sheath, the probe having a firstelectromagnetic field sensor embedded at a distal end thereof, whereineach of the at least three coils generates a signal when placed in anelectromagnetic field, wherein one of the at least three coils forms aplane perpendicular to the longitudinal axis along the longitudinallumen, and wherein the other two of the at least three coils form twoplanes, which are angled with respect to the longitudinal axis andapproximately perpendicular to each other.
 12. The system of claim 11,wherein the signal is indicative of a strength of the electromagneticfield and a position of the sheath.
 13. The system of claim 11, whereinthe at least three coils are positioned proximate a distal end of thesheath.
 14. The system of claim 11, wherein the sheath has a secondelectromagnetic field sensor embedded at a distal end thereof.
 15. Thesystem of claim 14, wherein the first and second electromagnetic fieldsensors are six degree-of-freedom sensors.
 16. The system of claim 15,further including an electromagnetic field generation device forcreating electromagnetic fields having a plurality of frequencies forinducing signals in the first and second electromagnetic field sensors.